8051u Minimum System Board (Two Versions!)

Similarities: 1. Both boards have all GPIO pins brought out except for P5.6 and P5.7. 2. The pinout order is the same (meaning if you design an extended version, the two versions are compatible). 3. Both boards bring out P3.1, P3.0 5V, and Gnd, allowing for quick programming via an XH2.56 to DuPont converter (although they are all on the board). 4. Both boards have reserved pads for AT24CXX (you can solder them on if you like). 5. Power LED indicator and GPIO-controlled LED. 6. Uses an LQFP-48 packaged 8051U. 7. Also includes a reverse breakdown diode for voltage regulation (probably overvoltage protection). 8. Also includes a 0805 self-resetting fuse. 9. Both MCUs operate at 3.3V. Differences: 1. You can clearly see that... One board uses the STC8H8K64U for downloading (yes, I cut a portion of the schematic for a two-in-one solution, and both serial ports are brought out, one just doesn't have an LED...). (Supports automatic power-off downloading!). The other uses USB-HID for downloading (I made it length-equalized). (This definitely doesn't support power-off downloading). This one uses fewer components than the previous schematic and board, but of course, it also has some inconveniences! 2. The board with the STC8H8K64U supports switching between 3.3V and 5V download levels!!!! Use a 0-ohm resistor, but you can only solder one at a time! One at a time! (You wouldn't want to burn out a new board because you soldered it wrong...) 3. Regarding the button differences, refer to the schematic (I don't want to type anymore QAQ). (Simply put, to allow the STC8H8K64U to update the USB to 2-TTL program, two buttons are used, so the one for the user is gone...) (You have three, right? One is for the RST...) 4. Boards with STC8H8K64U can only install one SD card and one AT24Cxx (you can't insert two even if you want...) 5. Boards with STC8H8K64U have two more Txd and Rxd communication indicator lights. Regarding the download method: omitted for those with TTL... Regarding USB download, based on the documentation, after all soldering is done, press and hold the Download button before plugging in.
 
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